Page Boundary Question

["Bryan Parkoff" <spam>]

    I understand that 6502 can only add one extra cycle if it is across page
boundaries.

    For example,

2000: A9 00    LDA #00
2002: F0 EC    BEQ 1FF0

    If BEQ is true, it will branch to $1FF0.  Extra cycle is supposed to be
added, but it didn't.

2080: A9 00    LDA #00
2082: F0 7F    BEQ 2103

    If BEQ is true, it will branch to $2103.  Extra cycle will be added.
($20)$82 + $7F will always show carry flag that will let cycle to know
before it is added.  How can 6502 know that ($20)$04 + $EC will not always
show carry flag?  Please explain.  It is what 6502 Reference Manual says
that branch can only add one extra cycle if carry flag is present.

Bryan Parkoff